In the related art, there is provided a vehicle seat slide device in which an upper rail thereof includes a bracket support having a pair of side walls and an upper wall connecting the respective side walls to each other.
For example, in a seat slide device disclosed in JP 2010-173487A (Reference 1), an upper wall thereof and each vertical wall are cut out. In this manner, a slit-shaped cutout portion which is open upward is formed in a bracket support of the upper rail. In addition, a nut member which can be screwed to a bolt inserted into the bracket support via a terminal of the bracket support is disposed inside the upper rail. Furthermore, a bracket includes a pair of vertical walls having an insertion hole into which the bolt is inserted and opposing each other. One side of the respective vertical walls is arranged at a position in contact with the terminal, and the other side is arranged inside the cutout portion. Then, this seat slide device has a configuration in which both vertical walls are interposed therebetween in an axial direction of the bolt based on a fastening force of the bolt screwed into the nut member so that the bracket is fixed to the upper rail.
However, in the configuration in which two vertical walls are interposed between the bolt and the nut as in the related art, there is a possibility that the respective vertical walls may be deflected due to the fastening force and a narrowed gap between both of these causes the bracket to tilt in the axial direction of the bolt. Then, this may cause a possibility that support rigidity of a seat may deteriorate. In this regard, there is still room for improvement.